ITTO20120988A1 - ARTIFICIAL LIGHTING SYSTEM TO SIMULATE A NATURAL LIGHTING - Google Patents

Description

DESCRIPTION

â € œSYSTEM OF ARTIFICIAL LIGHTING TO SIMULATE A NATURAL LIGHTINGâ €

The invention relates to an artificial lighting system. In particular, the invention relates to an artificial lighting system that simulates natural lighting. This lighting system can illuminate a room in which it is inserted, with effects very similar to the effects that would occur in the same room if there was an opening beyond which there are sky and sun.

It is known that artificial lighting systems are currently available for indoor environments which aim to improve the visual comfort of users. In particular, lighting systems are known that simulate natural lighting, that is the type of lighting present in open-air environments ("outdoor"). The well-known characteristics of outdoor lighting depend on the interaction between the light rays produced by the sun and the earth's atmosphere.

In the pending European patent application EP2304480, filed by the present Applicant, a lighting system is described which comprises a light source, suitable for generating visible light, and a panel containing nanoparticles. When in use, the panel receives the light rays coming from the source and acts as a so-called Rayleigh diffuser, that is, it diffuses the light rays in a similar way to what happens in the earth's atmosphere under clear sky conditions.

Further details relating to the panel referred to in the pending patent EP2304480 are described in the pending European patent application EP2304478, filed by the present Applicant. Furthermore, the pending patent application EP2304480 describes various embodiments of the panel, as well as various arrangements of the panel with respect to the light source, suitable for simulating various conditions of natural lighting, such as for example lighting conditions that are present in nature in the case of clear sky and i) sun at the zenith or ii) sun at the horizon.

The lighting system described in patent application EP2304480 simulates natural lighting since it generates, within the surrounding environment, direct light with a correlated low color temperature ("CCT"), which simulates sunlight and generates shadows in presence of illuminated objects; furthermore, the lighting system described in patent application EP2304480 simulates natural lighting by generating diffused light with high CCT, which simulates the light of the sky and generates blue shadows. Nevertheless, this lighting system does not perfectly reproduce in an observer the perceptual effects that he would have in the presence of a window overlooking the sky. In particular, this lighting system does not allow the observer to experience the visual perception of an unlimited depth of field.

Therefore, the present invention has the purpose of providing a lighting system capable of overcoming the limitations of the known state of the art, at least in part.

The invention provides an artificial lighting system as reported in the independent claims, possible advantageous implementations being the subject of the dependent claims.

For a better understanding of the invention, embodiments are now described purely by way of non-limiting examples and with reference to the attached drawings, in which:

Figures 1, 2 and 7 show schematic cross sections of embodiments of the present lighting system;

Figure 3 shows a schematic cross section of a possible lighting system different from the present lighting system;

- figures 4a and 4b schematically show perspective views of light sources;

figures 5a, 6 and 8 schematically show perspective views of parts of the present lighting system;

figure 5b shows a cross section of a reflecting element present in the part of the lighting system illustrated in figure 5a;

- figures 9a and 10 show perspective views of light sources;

figure 9b shows a cross section of a part of the light source illustrated in figure 9a; and - figure 11 shows a cross section of a part of an embodiment of the present lighting system.

In general, the Applicant observed that the ability of an observer to evaluate the distance of objects, and therefore the depth of field of the views that constitute a three-dimensional view, is based on multiple physiological and psychological mechanisms related to focusing, convergence binocular, binocular parallax, motion parallax, luminance, size, contrast, aerial perspective, etc. Some mechanisms can be significant compared to others both depending on the observation conditions (for example if the observer is moving or stationary, if he observes the landscape with one or two eyes, etc.) and depending on the characteristics of the view, these latter, for example, depending on the presence or absence of objects with a known size, distance or luminance, which serve as a reference to evaluate how far the observed element of the view is.

In particular, the Applicant noted that an observer observing a lighthouse through a window loses the ability to assess how far the lighthouse is, when the distance is greater than five meters (preferably seven meters), provided the surrounding background. the headlight is black and uniform. When these circumstances are met, the distance to the lighthouse cannot be determined by the observer. The ability to judge distances is diminished as i) precise focusing of a dazzling light source is difficult, which prevents the observer from using the focusing mechanism to assess the distance of the object and ii) binocular convergence is poorly effective as a tool for distance assessment, when the object is more than five meters away (preferably seven meters); furthermore, the ability to evaluate is diminished due to the inefficiency of other psychophysical mechanisms which are commonly active and effective in the case of long distances, such mechanisms being inhibited by the lack of further reference points.

The Applicant also noted that, when a Rayleigh diffusion panel is interposed between the observer and the lighthouse, the latter being surrounded by a uniform black background, the observer is induced to virtually perceive the lighthouse at a infinite distance. More specifically, the infinite distance perception effect is obtained if the observer observes the lighthouse through the Rayleigh diffusion panel, and the latter is completely and uniformly illuminated by the lighthouse, and if the real beacon-observer distance is at least five meters (preferably seven meters). This effect can be interpreted as a consequence of the so-called "aerial perspective", a perceptual mechanism induced by the Rayleigh diffusion panel. In fact, the color and intensity of the light scattered by the Rayleigh diffusion panel are virtually identical to the corresponding color and intensity of the sky light, where the intensity is evaluated relative to the intensity of the transmitted light. In particular, the so-called aerial perspective mechanism is related to the presence of a layer of air interposed between any object and the observer; the color and luminance of this air layer influence the evaluation of the object-observer distance, the object being perceived by the observer as arranged behind the air layer itself; this mechanism is dominant for large distances or, in general terms, when the other psychophysical mechanisms for the assessment of distance are impeded or not very effective.

The Applicant has also noted how the observer is induced to perceive the light emitted by the Rayleigh diffusion panel as coming from a virtually infinite distance, as long as the light from the beacon is within the observer's field of view. This effect can be interpreted considering that the Rayleigh diffusion panel acts as a secondary source of light radiation and that the observer can hardly assess how far it is from the plane of emission of this light radiation, given the high spatial uniformity of the radiation. light itself, which does not provide any visual reference point to observe. Therefore, the presence of the lighthouse in the field of view at a (physical) distance of five meters (preferably seven meters) affects the evaluation of the entire depth of field of the view, "dragging" the estimated position of the Rayleigh diffusion panel beyond the distance perception threshold by binocular convergence. This effect is related to the luminance of the lighthouse and to the fact that, in addition to the Rayleigh diffusion panel, the lighthouse itself is the only spatially localized element perceived by the observer. In practice, observing the Rayleigh diffusion panel, the observer's eyes are forced by the lighthouse to arrange themselves as if looking at an object very far away. The mind is therefore induced by this arrangement of the eyes to deduce that the object in the center of the visual field, that is the light emitted by the Rayleigh diffusion panel, is positioned very far from the real position of the panel itself. Furthermore, the effect of perceiving a diffused light source at a great distance from the observer is favored by the fact that the light diffused by the Rayleigh diffusion panel has the same color and luminance (with respect to the transmitted light) typical of light. of the sky. This effect, due to the aforementioned aerial perspective mechanism, is particularly effective, ensuring that the lighthouse is perceived at a virtually infinite distance. The Applicant has also noted how the effect described, that is the visual perception of an infinite depth of field (hereinafter referred to as the "breakthrough effect"), occurs regardless of the direction of observation through the Rayleigh diffusion panel.

In addition, the Applicant noted that the aerial perspective alone cannot perfectly ensure the breakthrough effect, if the lighthouse is outside the visual field, since other psychophysical mechanisms prevail, such as for example the focusing of scratches or edges of the Rayleigh diffusion panel.

Furthermore, the Applicant has noted how the aforementioned breakthrough effect is reduced if the lighthouse is positioned close to the Rayleigh diffusion panel, for example in the absence of mirrors or lenses that distance the virtual image thereof. In fact, in this case the distance to the lighthouse could be easily estimated by the observer, which would limit the depth of field in the whole view, despite the contribution of the aerial perspective. Similarly, the Applicant has noted that the aforementioned piercing effect is reduced if the lighthouse is not surrounded by a uniform black background. In fact, an observer can determine the distance from a background other than a uniform black background, thereby limiting the depth of field of the entire view, despite the contribution of the aerial perspective.

Having said all this, figure 1 shows an artificial lighting system 1, which will be referred to in the following, for the sake of brevity, as the lighting system 1.

In detail, the lighting system 1 includes a first light source 2, preferably directional, that is, capable of emitting light in a solid emission angle lower than 4Ï sterad. Furthermore, the first light source 2 emits light in the visible region of the spectrum, ie with wavelengths between 400 nm and 700 nm. Furthermore, the first light source 2 emits light (visible electromagnetic radiation) at a spectral width Î ”λ preferably greater than 100 nm, more preferably greater than 170 nm. The spectral width Î ”λ can be defined as the standard deviation of the wavelength spectrum of the first light source.

The lighting system 1 also includes a first diffuser panel 4, which for example is in the shape of a parallelepiped. In particular, the first diffuser panel 4 is delimited by a first surface S1 and by a second surface S2, parallel to each other; preferably, the first diffuser panel 4 is thin, i.e. its thickness w, measured along a direction perpendicular to the first and second surfaces S1, S2, has a squared value of no more than 5%, preferably 1%, of the area of the first and second surfaces S1, S2.

More particularly, in the embodiment illustrated in Figure 1, the first diffuser panel 4 functions as a so-called Rayleigh diffuser, i.e. as a panel which essentially does not absorb light in the visible range and which diffuses the light components more effectively. incident at short wavelengths with respect to components at long wavelengths, for example a panel which substantially does not absorb light in the visible range and which diffuses light rays at a wavelength Î "= 450 nm (blue) at least 1.2 times, preferably at least 1.4 times, more preferably at least 1.6 times more effectively than light rays at a wavelength Î »= 650 nm (red), wherein the diffusion efficiency is ̈ given by the ratio between the radiant power of the scattered light and the radiant power of the incident light. The optical properties and the microscopic characteristic of the Rayleigh diffusers are further described in detail in the patent application EP2304478 of the same Applicant. A further description of the microscopic elements is also provided in the following part.

In the embodiment illustrated in Figure 1, the first light source 2 is vertically aligned with the first diffuser panel 4, i.e. it is arranged along an axis H, which is perpendicular to the first and second surfaces S1, S2 and passes through the center of gravity of the latter (in Figure 1, the center of gravity of the first surface S1 is indicated with O). Furthermore, the first light source 2 fully illuminates the first diffuser panel 4. Embodiments in which the first light source 2 is arranged offset with respect to the center of gravity of the first and second surfaces S1, S2 are, however, possible, as described in that follows.

The lighting system 1 is optically coupled to an environment, for example a room 6 in the shape of a parallelepiped and bounded by a lower wall P1, an upper wall P2 and four side walls P1. In particular, without any loss of generality, it is assumed that the upper wall P2 has a cavity 8, which, seen from above, has the same shape as the first diffuser panel 4 and is completely occupied by the latter. In any case, the present invention is not limited to the shape and / or arrangement of the cavity 8; for example, according to further embodiments (not illustrated), the cavity can be formed within a side wall. Furthermore, the present invention is not limited to indoor use; therefore, embodiments are possible in which the lighting device 1 is used as a system for lighting similar to the daytime of outdoor environments, during the night. Therefore, the lighting system 1 can be coupled to an outdoor environment, that is an environment equivalent to a room, whose walls are black or arranged at an infinitely high distance.

The lighting system 1 comprises a support element 10 which defines, together with the first surface S1 of the first diffuser panel 4, an external volume V which is outside the room 6; the first light source 2 is placed inside the external volume V. Although not illustrated, there are possible embodiments in which the support element 10 is mechanically coupled to the room 6 in such a way that the external volume V It is also partially delimited by a wall of room 6, for example the upper wall P2.

The support element 10 is internally coated by an internal layer 12, made of a material capable of absorbing the incident light radiation; such material, for example, is a black colored material with an absorption coefficient in the visible range higher than 70%, preferably higher than 90%, more preferably higher than 95%, even more preferably higher than 97%. The internal layer 12 has the purpose of absorbing the incident radiation which comes, for example, directly from the first light source 2 or from processes of reflection and / or diffusion through the first diffuser panel 4, or from the room 6 through the first diffuser panel 4 Preferably, the volume V is internally covered in its entirety by the inner layer 12, with the exception of the first surface S1 of the first diffuser panel 4. In other words, the support element 10 and the inner layer 12 define a sort of dark box ; therefore, in what follows, reference will also be made to a dark box 10.

Referring again to the first diffuser panel 4 and assuming that a light beam is generated by a standard D65 CIE (International Commission of Illumination) point light source at a great distance from the first diffuser panel 4 (a beam, therefore, consisting of light rays parallel to each other) and is directed perpendicularly to the first surface S1, the first diffuser panel 4 separates this beam into four components, in particular in:

- a transmitted component, formed by light rays that pass through the first diffuser panel 4 and do not undergo significant deviations, i.e. light rays that undergo a deviation of less than 0.1 °, with a luminous flux that is a direct fraction of the flux overall light incident on the first diffuser panel 4;

- a forward diffusion component, formed by light rays coming out of the second surface S2 in long directions which are distributed around a direction perpendicular to the second surface S2 (with the exception of this perpendicular direction and the directions which differ from this perpendicular direction by an angle less than 0.1 °), with a luminous flux which is a diffused fraction of the total luminous flux incident on the first diffuser panel 4;

- a backward diffusion component, formed by light rays exiting from the first surface S1 along directions which are distributed around a direction perpendicular to the first surface S1 (with the exception of this perpendicular direction and directions which differ from this perpendicular direction by a angle less than 0.1 °), with a luminous flux which is a diffuse fraction of the overall luminous flux incident on the first diffuser panel 4; And

- a reflected component, formed by the light rays that exit, or originate, from the first surface S1, along a direction at a specular angle (for example, perpendicular or different from the perpendicular by an angle of less than 0.1 °, in the present case ) with respect to the first surface S1, with a luminous flux which is a direct fraction Ï of the overall luminous flux incident on the first diffuser panel 4.

All this said, the optical properties of the first diffuser panel 4 are such that:

- diffuse is in the range 0.05-0.5, preferably 0.07-0.4, more preferably 0.1-0.3, still more preferably 0.15-0.25;

- the mean correlated color temperature ("CCT") CCT_ï ́diffuse of the forward scatter component is significantly higher than the mean correlated color temperature CCT_ï ́direct of the transmitted component, i.e. CCT_ï ́diffused> h * CCT_ï ́directwith h = 1,2, preferably h = 1.3, more preferably h = 1.5;

- the first diffuser panel 4 does not significantly absorb the incident light, i.e. the sum ï ́direct + ï ́diffused + Ï direct + Ï diffusedà is at least equal to 0.8, preferably 0.9, more preferably 0.95, again more preferably at 0.97;

- the first diffuser panel 4 diffuses mostly forward, i.e. ï ́diffused> Î · * Ï diffuse, in which Î · is at least equal to 1,1, preferably Î · = 1,3, more preferably Î · = 1.5, even more preferably Î · = 2; And

- the first diffuser panel 4 has a low reflection, ie direct <0.09, preferably <0.06, more preferably <0.03, even more preferably <0.02.

In greater detail, the first diffuser panel 4 comprises a solid matrix of a first material (for example a resin having excellent optical transparency, such as thermoplastic resins, thermosetting resins, photo-curable resins, acrylic resins, epoxy resins, polyester resins, polystyrene resins , polyolefin resins, polyamide resins, polyimide resins, polyvinyl alcohol resins, butyral resins, fluorine-based resins, vinyl acetate resins or plastics such as polycarbonate, liquid crystal polymers, polyphenylene ether, polysulfone, polyether sulfone, polyarylate, amorphous polyolefin or their mixtures or copolymers), in which nanoparticles of a second material are dispersed (for example, an inorganic oxide such as ZnO, TiO2, ZrO2, SiO2, Al2O3), this second material having a refractive index different from the refractive index of the first material. Both the first and the second material basically do not absorb electromagnetic radiation in the range of visible wavelengths.

Furthermore, in the embodiment illustrated in Figure 1, the first diffuser panel 4 is uniform, in the sense that, given any point of the first diffuser panel 4, the physical characteristics of the first diffuser panel 4 at that point do not depend on the point itself. . Furthermore, the first diffuser panel 4 is monolithic, that is, the solid matrix does not present any discontinuity due to bonding or mechanical coupling. These characteristics of the first diffuser panel 4, however, are not necessary for the purposes of the present invention, although they make the first diffuser panel 4 easier to produce.

More specifically, nanoparticles can be monodisperse. The nanoparticles can be spherical or other shaped. The effective diameter D of the nanoparticles (for a definition in the case of non-spherical shape see below) falls within the range [5 nm-350 nm], preferably [10 nm-250 nm], more preferably [40 nm-180 nm ], even more preferably [60 nm-150 nm], in which the effective diameter D is given by the product of the diameter of the nanoparticles and the refractive index of the first material.

Furthermore, the nanoparticles are distributed inside the first diffuser panel 4 in such a way that their areal density, i.e. the number N of nanoparticles per square meter, i.e. the number of nanoparticles within a volume element delimited by a part of the first surface S1 having an area of 1 m2, you satisfy the condition Nâ ‰ ¥ Nmin, where:

where Î1⁄2 is a dimensional constant equal to 1 meters <6>, Nminà ̈ expressed as number / meters2, the effective diameter D is expressed in meters and m is equal to the ratio of the refractive index of the second material and the refractive index of the first material.

Preferably, the nanoparticles are homogeneously distributed, at least as regards the areal density, i.e. the areal density is substantially uniform across the first diffuser panel 4, but the distribution of the nanoparticles can vary through a direction perpendicular to the first and second surface S1 , S2. The areal density varies, for example, by less than 5% compared to the average areal density. The areal density is here intended as a quantity defined on areas greater than 0.25 mm².

Alternatively, embodiments are possible in which the areal density varies, so as to compensate for the differences in illumination on the first diffuser panel 4, when illuminated by the first light source 2. For example, the areal density N (x, y) in the point (x, y) inside S1 can be correlated to the illuminance I (x, y), produced by the first light source 2 at point (x, y), through the equation N (x, y) = Nmedia * Imedia / I (x, y) ± 5%, where Nmedia and Imedias are the illuminance and the areal density calculated on average, the latter quantities being calculated on the average on the first surface S1.In this case, the luminance of the first panel diffuser 4 is equalized on the first diffuser panel 4, despite the non-uniformity of the illuminance profile of the first light source 2 on the first diffuser panel 4.

In the small D limit and reduced volume fraction (ie, thick panels), an areal density Nâ ‰ ˆNmin is expected to produce a diffusion efficiency of about 5%. As the number of nanoparticles per unit area increases, the diffusion efficiency is expected to increase proportionally to N, leading to multiple diffusions or interference (in case of a high volume fraction), which could compromise the quality. of color. The choice of the number of nanoparticles is therefore determined by the search for a compromise between the diffusion efficiency and the desired color, as described in detail in the patent application EP2304478. Furthermore, as the size of the nanoparticles increases, the ratio Î Furthermore, as Î · increases, the opening of the diffusion cone forward is reduced. Therefore, the choice of Î · is determined by the search for a compromise between having a diffused light at wide angles and minimizing the flow of light diffused backwards. Moreover, in a per se known way, an antireflection layer (not shown) can be deposited on the first and on the second surface S1 and S2, in order to reduce direct Ï to a minimum; by doing so, the luminous efficiency of the lighting system 1 increases and the visibility of the first diffuser panel 4 (as a physical element) by an observer in room 6 is reduced.

However, embodiments are possible in which the nanoparticles do not have a spherical shape; in this case, the effective diameter D can be defined as the effective diameter of the equivalent spherical particles, ie the effective diameter of the spherical particles having the same volume as the above mentioned particles.

Furthermore, embodiments are possible in which the nanoparticles are polydisperse, i.e. their effective diameters are characterized by an N (D) distribution. This distribution describes the number of nanoparticles per unit area and unit range of effective diameter in proximity to the effective diameter D (i.e., the number of particles per unit area having a D 2 <effective diameter between D1 and D2 is equal to > ND2 <ï €> D 1 <ï € 1⁄2>

DN (D) dD.

1

These effective diameters can fall within the range [5 nm-350 nm], ie the distribution can be non-zero in this range. In this case, considering that the diffusion efficiency increases approximately, i.e. within the limit of small particles, with the sixth power of the diameter of the nanoparticles, the polydisperse distribution acts roughly as a monodisperse distribution with a representative diameter Dâ € ™ effdefined as:

in which

Indeed it can be selected so as to fall within the range [5 nm-350 nm], preferably [10 nm-250 nm], more preferably [40 nm-180 nm], even more preferably [60 nm-150 nm].

Furthermore, the first diffuser panel 4 is at a distance d from the first light source 2, measured along the axis H. This distance d can be varied according to the expected position of the observer inside the room 6, so that the distance between the expected position of the observer and the first light source 2 is at least five meters, preferably seven meters. For example, in the case of a ceiling type application, the distance d can be equal to three meters. As a precaution, the distance d can be equal to five meters, if the observer is very close to the second surface S2.

According to a different embodiment, illustrated in Figure 2, the first light source 2 is still arranged inside the external volume V, but is arranged staggered, i.e. laterally with respect to the first diffuser panel 4, i.e. it is not intercepted. from no line that passes through the first diffuser panel 4 and is parallel to the H axis. Furthermore, the lighting system 1 includes a reflective system 20, which includes a first mirror 22 and forms a light path connecting the first light source 2 to the first diffuser panel 4; in other words, the light rays generated by the first light source 2 are conveyed by the reflecting system 20 onto the first surface S1. The first mirror 22 determines a last curve (ie a last change in direction) of the light path before the first diffuser panel 4.

In addition, the first light source 2 and the reflecting system 20 are such that the first diffuser panel 4 is completely illuminated by the light rays coming from the first light source 2. Furthermore, for reasons that will be described more accurately below, the first diffuser panel 4 and the reflecting system 20 are arranged in such a way as to satisfy the following geometric condition. There is no pair consisting of a light beam RL1 and a light beam RL2 such that:

- the light beam RL1 passes through the first diffuser panel 4 (for example, coming from room 6) or originates from the first diffuser panel 4; And

- the light ray RL2 is the reflection of the light ray RL1 from the reflecting system 20 and is directed so as to engrave again on the first surface S1.

The aforementioned geometric condition on the light rays RL1 and RL2 is equivalent to stating that no light ray generated inside the room 6 and which intersects the first surface S1 in a first point can be subsequently reflected by the reflecting system 20 in such a way as to affect again on the first surface S1 at a second point. Still in other words, the reflecting system 20 is arranged in such a way that all incoming light rays coming from the first surface S1e affect the reflecting system 20 are reflected on the inner layer 12, regardless of the position within the first surface S1da which the incoming light rays are emitted.

The aforementioned geometric condition relating to the light rays RL1 and RL2 leads to a reduction in the volume occupied by the lighting system 1, mainly in terms of the volume occupied outside the room 6, without damaging the quality of the lighting. In particular, the lighting system 1 has a reduction in the space occupied vertically, that is, measured along the H axis. Given that a reduced vertical dimension is a prerequisite for a large number of applications, the aforementioned geometric condition allows to obtain the breakthrough effect in a large number of situations of practical interest. For the sake of brevity, the reference to the vertical dimension of the occupied space will generally be omitted from now on.

In greater detail, in addition to reducing the space occupied, the mutual arrangement of the reflecting system 20 and of the first diffuser panel 4 prevents the occurrence of two phenomena that could compromise the natural quality of the lighting.

As shown in Figure 3, if the aforementioned geometric condition relating to the light rays RL1 and RL2 were violated, the following conditions would occur:

- a light ray IR1 generated by the first light source 2 affects the reflecting system (here indicated with the reference number 30) and is conveyed to the first diffuser panel 4, passes through the first diffuser panel 4 and reaches the observer; And

- a light ray IR2 generated by the first light source 2 affects the reflecting system 30 for the first time, it is conveyed for the first time on the first diffuser panel 4, it is partially reflected due to the Fresnel reflection from the first surface S1, affects the system reflective 30 a second time, it is conveyed a second time on the first diffuser panel 4, crosses the first diffuser panel 4 and reaches the observer from a different direction with respect to the light beam IR1.

In this case, the observer could experience the sight of two different images of the first light source 2, which are visible along different directions. The first image is the image formed by IR1 and all the light rays close to IR1, that is, by the light rays that have crossed the first diffuser panel only once. The second image is the image formed by the light ray IR2 and by all the light rays close to IR2, ie the rays which, having been partially reflected by the first surface S1, are redirected by the reflecting system 30 towards the observer. Since the Fresnel reflection redirects only a part (for example, about 4% for each surface of the first diffuser panel 4, for almost perpendicular incidence and for the PMMA material), the second image of the first light source 2 is weaker of the first. Nevertheless, its illumination intensity is still very high; therefore, an observer would perceive the difference with respect to natural lighting, which is evidently characterized by the presence of a single image of the sun.

Similarly, if the aforementioned geometric condition relating to the light rays RL1 and RL2 is not satisfied, the light rays coming from the room 6 and of any color could pass through the first diffuser panel 4, be reflected by the reflecting system 30 and re-enter the room. 6 after passing through the first diffuser panel 4 again. In this case, an observer could perceive the presence of luminous objects having different colors from the color of the first diffuser panel 4, as if they were arranged behind the first diffuser panel 4. Furthermore, given the so-called backscatter, the first diffuser panel 4 itself would be visible to the observer not only directly, but also through the reflecting system 30; in practice, the first diffuser panel 4 would generate a luminous disc, spatially delimited by the mirror frame, which would ruin the uniformity of the background. In addition, an observer might notice the presence of the reflective system 30 given the rapid change in luminance that could occur at the edges of the mirror. All these effects would make the lighting unnatural, the image of the first diffuser panel 4 being different from that of the natural sky. Furthermore, the perception of the objects or mirrors in the background of the first diffuser panel 4 would prevent the breakthrough effect from being obtained.

All of this said, embodiments are possible in which, as illustrated in Figure 2, the first mirror 22 is flat and parallel to the first diffuser panel 4 (i.e. parallel to the first and second surfaces S1 and S2), so that the volume busy is minimized.

Furthermore, regardless of the shape and angle of inclination of the first mirror 22, the first light source 2 and the first mirror 22 are arranged in such a way that, if the surface of the first mirror 22 is indicated as the reflecting surface Sr, the center of gravity O of the first surface S1 and the center of gravity O 'of the reflecting surface Sr can be connected by a line having an angle of incidence AO with respect to the axis H which is between 40 ° and 65 °, preferably between 42 ° and 50 °, and which more preferably it is around 45 °. In this way, a compromise is obtained between the minimization of the space occupied vertically by the lighting system 1, which is reduced when the angle of incidence AO increases, and the minimization of light losses due to the partial reflection that occurs. checks in the first diffuser panel 4, which increases when the angle of incidence AO increases, in the hypothesis that the first diffuser panel 4 has a refractive index basically equal to 1.5 and that the angle of incidence AO is greater than 45 °. It is worth noting that the advantage of illuminating the first diffuser panel 4 at an angle of incidence AO substantially equal to 45 ° also applies to all possible embodiments, including those described below and those without any mirror.

The Applicant has also verified that, when the first mirror 22 is flat, the vertical space occupied by the lighting system 1 is reduced to a minimum for any angle of incidence AO, provided that the first mirror 2 is parallel to the first panel. diffuser 4.

Before continuing with the description, the "carrier beam" is defined as the bent light path that connects the center of gravity O "of the emission surface Sf (defined below) of the first light source 2 to the center of gravity O of the first surface S1, through the reflecting system 20 , or the shorter of these light paths, if there is more than one light path; there is only one light path if the reflective system 20 is designed as an optical imaging component.

In addition, a Cartesian reference system is introduced, such as a reference system having an origin in the center of gravity O of the first surface S1e comprising an x axis and a y axis lying in the plane defined by the first surface S1e are arranged in such a way that the y axis is perpendicular to the plane of incidence of the carrier beam on the reflecting surface Srd of the first mirror 22 (i.e. the plane containing the two segments of the carrier beam that come into contact with the first mirror 22, as well as the line perpendicular to the reflecting surface Sr at the point of contact).

Regardless of the shape and angle of inclination of the first mirror 22, embodiments are possible in which the first surface S1 has a rectangular or at least elongated shape, with its major axis coinciding with the y axis. The Applicant has verified that these embodiments allow to satisfy the geometric condition relating to the light rays RL1 and RL2 with a lower height of the lighting system 1 along the axis H, with respect to the cases in which the first diffuser panel 4 is not It is elongated or it is elongated along the x axis, with the same area of the first diffuser panel 4 and the angle of incidence AO. In other words, these embodiments allow to maximize the area of the first diffuser panel 4 for a given height of the lighting system 1 and a given angle of incidence AO. In fact, the Applicant has noted that, for a given angle of incidence AO, the maximum width of the first diffuser panel 4 along the x axis is proportional to the minimum height of the lighting system 1 along the H axis, the coefficient of proportionality being close to 1 when the angle of incidence AO is close to 45 °.

The Applicant has also noted that the natural quality of the lighting is further improved if the first light source 2 has an Srcircular (figure 4a) or elliptical (figure 4b) emission surface. Since the first light source 2 is directional, it is characterized by a main direction, which is the direction of the absolute maximum of the light intensity and by a main plane, defined here as the plane, perpendicular to the main direction, in where the absolute maximum of luminance is present. That said, the emitting surface is the part of the main plane where the luminance along the main direction is greater than 10% of this absolute maximum of luminous intensity. The Sfà emission surface is called circular or elliptical if there is a circumference or an ellipse that encloses it and has an area greater than the area of the emission surface Sf, by no more than 30%, preferably not more than 20%, most preferably not more than 10%.

All this said, the light rays strike the first surface S1 in corresponding points of incidence and form corresponding angles of incidence with the lines perpendicular to the first surface S1e passing through the points of incidence. That said, the reflecting system 20 and the arrangements of the first light source 2 and of the first diffuser panel 4 are such that, given:

- a light beam RL3 which connects, through the reflecting system 20, the center of gravity O "of the emission surface Sfal center of gravity O of the first surface S1e forms an angle Î ̧1 with respect to a line perpendicular to the first surface S1e passing through the center of gravity O of this' last; e

- a light beam RL4 which connects, through the reflecting system 20, the center of gravity O "of the emission surface Sfad to a point of the first surface S1 which is spaced by a distance X from the center of gravity O of the latter, and which forms an angle Î ̧2 with respect to a line perpendicular to the first surface S1e passing through this point;

we have:

tan (Î ̧1 - Î ̧2) â ‰ ¤ X cos (Î ̧1) / L

where L is at least equal to three meters and, preferably, X << L, for example X <10 cm. Preferably, L is at least equal to four meters; even more preferably, L is at least equal to five meters. Note that this condition is also satisfied by the embodiment illustrated in Figure 1, provided the aforementioned distance d of the first diffuser panel 4 from the first light source 2 is equal to L.

In this way, the light rays strike the first surface S1 with almost parallel directions, similar to what happens in nature. Furthermore, this condition can also be satisfied when the first light source 2 is less than L at a physical distance from the first diffuser panel 4, as long as the reflecting system 20 includes converging mirrors, i.e. mirrors designed to form a virtual image of the first light source 2 at a greater distance than the physical distance.

The Applicant also noted that the natural lighting quality improves when the maximum luminance of the first light source 2 is greater than 106 cd / m2, preferably 0.1 * 106 cd / m <2>, more preferably than 1 * 10 <6> + cd / m <2>, even more preferably than 10 * 106 cd / m <2>. For these values, in fact, the first light source 2 generates a sufficient glare so that the same source is difficult to observe, thus preventing the observer from assessing the distance of the source through the focusing mechanism of the eyes. These luminance values then help to achieve the infinite pierce effect. Furthermore, glare makes it difficult to detect possible non-uniformities in the luminance profile of the first light source 2, making it difficult to detect the differences between the image of the first light source 2 and the image of the sun.

The Applicant has also verified that the natural quality of the lighting improves if the size and shape of the first light source 2 are such that, given a light ray that connects the perimeter of the emission surface Sfal center of gravity O of the first surface S1, the The angle it forms with the aforementioned light ray RL3 is less than 4 °, preferably 3 °, more preferably 1.2 °, and even more preferably 1.0 °. In fact, the natural quality of the lighting improves when the lower values of this angle are associated with the higher values of luminance, this condition allowing to obtain a more natural perception.

As illustrated in Figures 5a and 5b, regardless of the details of the first diffuser panel 4, the first mirror 22 may be a concave curved mirror, for example a concave curved mirror having a parabolic curvature. In particular, as illustrated in Figures 5a and 5b, the first mirror 22 can be shaped as a part of a circular paraboloid, i.e. a surface obtained by rotating a generating parabola around its axis A, so that the intersection with any plane which includes the axis A defines the same generating parabola. In particular, the part of the circular paraboloid is obtained by dividing a part of the surface of the circular paraboloid with a secant plane that crosses the A axis forming an angle other than 90 °. For the sake of brevity, from now on, we will refer to the circular paraboloid without explicitly mentioning that the mirror is formed by a part of the circular paraboloid.

According to the present embodiment, the first light source 2 is arranged in the focus of the circular paraboloid; more precisely, the center of gravity Oâ € of the emission surface Sf of the first light source 2 is arranged in the focus of the circular paraboloid, therefore the light rays coming from this center of gravity and reflected by the circular paraboloid affect the first surface S1 with propagation directions all parallel to the axis A. In this way, the observer perceives the first light source 2 as if it were arranged at a virtually infinite distance, similarly to what happens with the sun, thus improving the natural quality of illumination. In other words, the virtual image of the first light source 2 is at an infinite distance from the observer.

Furthermore, the size of the first light source 2 perceived by the observer is given by the size of the image of the first light source 2 on the retina and depends only on the physical size of the first light source 2 and on the magnification of the optical telescopic system formed by the lens. of the eye and the circular paraboloid; this optical telescopic system has an image plane and an object plane which are arranged, respectively, in the focus of the lens of the eye and in the focus of the circular paraboloid. The aforementioned magnification is given by the ratio between the focus of the lens of the eye and the focus of the circular paraboloid; therefore, the size of the first light source 2 perceived by the observer does not depend on the distance of the observer from the lighting system 1. Therefore, this further condition contributes to creating a natural lighting effect, since the perceived dimension of the sun does not depend on the position of the observer.

The Applicant has also noted that if the emission surface Sfà in the shape of a circle, the image of the first light source 2 perceived by the observer is still circular, because the optical system illustrated in Figure 5a does not distort the image.

The embodiment illustrated in figure 5a is characterized by the fact that the vertical space occupied by the lighting system 1 is almost equal to the size of the first diffuser panel 4 along the x axis, in the case in which the light rays reflected by the paraboloid circular incident on the first diffuser panel 4 at 45 °, and the aforementioned geometric condition is satisfied.

According to a variant, illustrated in Figure 5a, the first and second surfaces S1 and S2 of the first diffuser panel 4 have an elliptical shape, this shape being enclosed by the projection of the circular paraboloid 22 on the xy plane along the direction given by the axis A. Therefore, the first and second surfaces S1 and S2 can be circumscribed by the luminous disc SP formed by the circular paraboloid in the xy plane, thus reducing light losses. Furthermore, the first mirror 22 is cut in such a way as to accept a light beam having a circular divergence, that is, it is cut in such a way that its projection on the plane orthogonal to the line connecting the center of gravity O "of the emission surface Sfe the vertex of the circular paraboloid has a circular shape or at least circumscribes a circle with good approximation However, other shapes of the first mirror 22 are also possible, for example an elongated shape along the y direction.

The use of the circular paraboloid implies that the light entering room 6 through the first diffuser panel 4 projects a luminous disk on the floor of room 6 having the same shape and the same size as the first diffuser panel 4, as happens with sunlight through a window, thus contributing to the natural lighting effect. Furthermore, since the observer is able to evaluate the distance of a generic light source based on the divergence of the light beam it generates, the lighting system 1 illustrated in figure 5a creates an effect of great depth of field, even if the first light source 2 is not directly in the observer's field of view.

As illustrated in Figure 6, the first mirror 22 can be shaped as part of a paraboloid with cylindrical symmetry, that is, as part of a parabolic cylinder, this part being obtained by intersecting the parabolic cylinder with three secant planes. In detail, it is known that, given a generating parabola and a reference line R, the parabolic cylinder is the ruled surface formed by the lines parallel to the reference line R and incident on the generating parabola; in other words, the parabolic cylinder is obtained by translating the generating parabola along the reference line R. In what follows, the reference line R is also called the cylindrical axis.

In the embodiment illustrated in Figure 6, the parabolic cylinder is obtained by translating the generating parabola along a direction parallel to the x axis. Furthermore, the generating parabola has its vertex in the xH plane and its axis A oriented along a line that is mirrored to the line connecting the center of gravity O of the first surface S1 and the center of gravity O 'of the reflecting surface Srdel first mirror 22. In this embodiment, a plane tangent to the parabolic cylinder in the vertex of the generating parabola is parallel to the xy plane. Furthermore, two of the three secant planes are, for example, parallel to the yH plane, while the third plane is, for example, substantially parallel to the xy plane. All this said, from now on, for the sake of brevity, we will refer to the parabolic cylinder, without explicitly mentioning that the mirror is formed by a part of the parabolic cylinder.

In the embodiment illustrated in Figure 6, the parabolic cylinder is laterally spaced along the x axis, with respect to the H axis, so that the angle of incidence AO is substantially equal to 45 °.

In greater detail, the center of gravity O "of the emission surface Sfà is arranged in the xH plane, close to the line formed by the foci of the parabolas that form the parabolic cylinder, in the position that ensures the best collimation of the light rays directed towards the first diffuser panel 4 , as regards the propagation of the rays in the plane containing the y axis and the center of gravity of the parabolic cylinder, and more generally as regards the propagation of the rays in all the planes that intersect the first diffuser panel 4 along lines parallel to the y axis In what follows, for simplicity, the mean divergence in these latter planes is referred to as the divergence along the direction of the y axis.

The embodiment illustrated in Figure 6 allows to use a first diffuser panel 4 which is considerably longer, along the y axis, rather than along the x axis, thereby maximizing the area of the first diffuser panel 4 and hence the angles at which the observer perceives the breakthrough effect. More precisely, such a large elongation of the first diffuser panel 4 is possible since the embodiment is based on the use of a mirror which has a large elongation in the direction of the y axis, while maintaining a limited (output) divergence in the same direction as the y axis. More specifically, the Applicant has noted that the perceived size of the first light source 2 along the direction of the y axis, that is, the diameter of the emission surface Perceived along the direction of the y axis, does not depend on the distance between the observer and the first light source 2, or it depends on this distance very slightly. As regards the size of the first light source 2 perceived by the observer along the direction of the x axis, it depends on the position of the observer and decreases with distance. Therefore, to ensure the perception of a circular shape of the first light source 2, it is possible to adopt a light source with an elliptical emission surface Sf, in which the eccentricity of the ellipse is fixed as a function of a predicted point of observation inside the room 6.

A further advantage provided by the use of a parabolic cylinder is the fact that this type of mirrors are easy to make, as they can be obtained using a flat mirror sheet, ie an aluminum mirror sheet. Furthermore, referring to an observer in a vertical position and observing the first light source 2 from a central position, i.e. through the center of gravity O of the first surface S1, and therefore with the eyes aligned along the direction of the y axis, he will perceive the first light source 2 at a great distance, due to the fact that the convergence of its eyes works only in the planes containing both eyes (ie the direction of the y axis), where there is a high convergence. This occurs regardless of how much the divergence of the rays is in the orthogonal direction.

In a different embodiment (not shown), the lighting system 1 is mounted in such a way that the first diffuser panel 4 is parallel to a vertical wall, rather than to a ceiling, so that the light beam coming from the first light source 2 enters room 6 parallel to the floor and at an angle of approximately 45 ° to the vertical wall. In this embodiment, the parabolic cylinder is obtained by translating the generating parabola in a direction parallel to the y axis, rather than the x axis, this being the configuration that allows the maximum perception of depth for an observer, whose eyes are aligned along the x axis. Also in this case, given a height of the lighting system 1 beyond the vertical wall, the maximum area of the first diffuser panel 4 can be obtained by adopting an elongated shape in the direction of the y axis.

In a different embodiment, the reflecting system 20 may include a second mirror 24, as illustrated for example in Figure 7. That is, the aforementioned first mirror 22 may be a mirror of a plurality of mirrors of the reflecting system 20, which determines the last curve of the light path, along which the light rays generated by the first light source 2 are conveyed to the first diffuser panel 4.

The second mirror 24 is optically interposed between the first mirror 22 and the first light source 2. In this case, the aforementioned geometric condition does not vary, since this condition refers to the overall reflecting system 20. It is therefore irrelevant whether the light ray RL2 is generated by reflection of the light ray RL1 only on the first mirror 22 or on the first and second mirrors 22, 24. Similarly, the reflecting system 20 can include further reflecting elements (not shown).

Any one between the first and second mirrors 22, 24 can be flat or have a different shape. In particular, as illustrated in Figure 8, embodiments are possible in which both the first and second mirrors 22, 24 are shaped as parts of two corresponding parabolic cylinders, which are generated by generating parabolas which are located in orthogonal planes, and which are translated along orthogonal directions and therefore perform the collimation of the light in orthogonal planes. In the present embodiment, for example, the first mirror 22 is similar to the parabolic cylinder illustrated in Figure 6, while the second parabolic cylinder, which forms the second mirror 24, is obtained by considering a second generating parabola in the xH plane and translating it along the direction of the y axis, thus obtaining a reduction in the divergence of the beam in the xH plane. Furthermore, the Applicant has verified that good collimation is obtained in all directions for the light rays reflected from the second mirror 24 towards the first mirror 22, when the second generating parabola has its axis oriented in a direction substantially parallel to the axis of the generating parabola of the first mirror 22, provided that the two parabolic cylinders are arranged in such a way that they share a common focus (or, more precisely, in such a way that the generating parables share a common focus, in which the position of the focus of the generating parabola of the first mirror 22 accounts for the reflection by the mirror 24) and the first light source 2 is substantially arranged in this common focus.

The embodiment illustrated in Figure 8 allows the use of a diffuser panel having a length along the y axis which is considerably greater than the length along the x axis, and therefore allows the area of the first panel to be maximized. diffuser 4, the vertical space occupied by this embodiment being the same as that occupied in the case of a square panel. Furthermore, this embodiment allows to generate a light beam that affects the first surface S1 with a reduced divergence along both the x and y axes (i.e. along the planes that intersect the xy plane along lines that are parallel to the x axis and the y axis , respectively). Therefore, the transmitted light rays have a divergence similar to the sun's rays. This condition helps create a remarkable depth of field perception even when the first light source 2 is not in the observer's field of view. Furthermore, since the first light source 2 is arranged near the common focus, the size of the first light source 2 perceived by the observer does not depend on the distance. Finally, the illumination of a diffuser panel elongated along the direction of the y axis is here made possible starting from a light beam which affects the second mirror 24 substantially with the same divergence both in the incidence plane and in the orthogonal plane, that is, effectively using a light source that generates a light beam having a cross section similar to a square. This result, which is achieved by performing the divergence reduction of the initial beam in two separate steps in the two orthogonal directions, represents an advantage over the case of a single parabolic cylinder, for which asymmetrical beams are required, as described below.

Regardless of the details of the first diffuser panel 4 and of the reflecting system 20, the first light source 2, as explained above, can have an emission surface Sf with a circular or elliptical shape. In particular, the emission surface Sf can have an elliptical shape if the reflecting system 20 includes at least one paraboloid with cylindrical symmetry, so that the different magnifications introduced along the x and y axes are compensated, thus allowing the creation of a disk. circular light on the observer's retina.

As illustrated in Figures 9a and 9b, the first light source 2 can be formed by a series of emission devices 50. Each emission device 50 is formed by a LED source 52 and a corresponding compound parabolic concentrator ("CPC") 54 of the rectangular type, which has an inlet opening IN and an outlet opening OUT; the inlet opening IN and the outlet opening OUT can be respectively shaped as a first and a second rectangle, parallel and aligned with each other, the first rectangle having a smaller area than the second rectangle. Furthermore, the first rectangle has a different ratio between the lengths of its axes of symmetry than the second rectangle. For example, the first rectangle has a higher ratio, ie it is more elongated, than the second. The LED source 52 can be formed by an array of LED emitters (not shown) and is arranged near the corresponding input opening IN, so that the radiation emitted by the LED source 52 is coupled to the concentrator CPC 54 through the opening IN, and exits through the OUT port. However, other types of reflective concentrators are possible; similarly, it is possible to use light emitting devices other than LEDs.

The light beam generated by each emission device 50 has a rectangular cross section, its divergence being maximum in the plane containing the axis of the beam itself, i.e. containing the optical axis 56 of the pair formed by the concentrator 54 and the LED source 52 corresponding, and the greater of the symmetry axes of the rectangle defined by the outlet opening OUT, indicated with the reference number 57 in Figure 9a. In the case of a different output aperture OUT, the plane of maximum divergence would be defined by the direction of elongation, that is, by the direction of maximum extension of the output OUT, and by the optical axis 56.

The amount of divergence of the beam in each between the plane of maximum divergence and its orthogonal plane (also the latter containing the optical axis 56) progressively decreases with the ratio between the lengths of the corresponding side of the input rectangle, dIN, and of the corresponding side of the output rectangle, dOUT, and is in particular equal to the double of the arcsine of this ratio, that is arcsine (dIN / dOUT). In this regard, not only the areas, but also the shapes of the inlet and outlet openings must be different, in order to ensure different divergences in the two orthogonal planes.

The size of the inlet opening IN should be chosen to enclose the LED source 52. In the embodiment of Figures 9a and 9b, each concentrator 54 has a funnel-like shape and is formed by four parabolic reflective surfaces , each of which is one-dimensional curved and has a generating parabola which is arranged in the plane of maximum divergence or in its orthogonal plane, all the generating parabolas having their foci in the entrance plane in which the opening of IN input. Furthermore, the four parabolic reflective surfaces have the same length along the direction of the optical axis 56.

According to an embodiment, all the emission devices 50 are the same, and the concentrators 54 are arranged in such a way that the inlet openings IN are in the same inlet plane P_IN and the outlet openings OUT are in the same outlet plane P_OUT. In particular, the concentrators 54 are arranged close to each other, with the outlet openings OUT adjacent to each other, that is, they are tightly packed, so that the maximum average luminance of the emission surface is guaranteed; furthermore, the number and arrangement of the concentrators 54 are such that the surface formed by the union of all the outlet openings OUT resembles a circular surface, although embodiments are possible in which the compound surface resembles an elliptical shape. Finally, all the emission devices 50 are arranged so as to have their axes 56 oriented in the same direction. In this circumstance, the first light source 2 has its own "plane of greatest divergence", which is the plane containing the center of gravity O "of the emission surface Sfe which is parallel to the planes of maximum divergence of the emission devices 50 furthermore, the first light source 2 has an "axis of greatest divergence" 58, given by the intersection between the plane of greatest divergence of the first light source 2 and the emission surface Sf of the first light source 2. Even if the axis of greater divergence has been introduced with reference to the case of a plurality of rectangular concentrators 54, it is evident that other forms of concentrators 54 similar to a funnel and having elongated outlet openings along the parallel axes 57 lead to a light source still having a axis of greatest divergence, which is parallel to axis 57.

The first light source 2 illustrated in Figures 9a and 9b allows to decouple the characteristics of the light beam, and in particular the shape of its cross section and its divergence, from the shape of the emission surface Sf, without introducing any loss. In the present case, in which the emission devices 50 generate identical "unit light beams" having a rectangular cross section, the distances between the centers of the outlet openings OUT are reduced with respect to the width of the composite light beam formed by the sum of all the beams unitary light, this sum occurring due to the propagation of the composite beam and the divergence of each unitary light beam. In practice, the unitary light beams combine into a single composite light beam that has the same rectangular cross section and divergence as a single unitary light beam. In other words, at distances which are considerable with respect to the diameter of the emission surface Sf, the composite light beam has the same shape and divergence as the beam generated by a single emission device 50, since it is formed by a plurality of identical unit light beams that are slightly offset from each other. Therefore, the embodiment illustrated in Figures 9a and 9b allows to generate a composite beam having a section, in a plane perpendicular to the axis of the composite beam itself and at a desired distance from the first light source 2, which is a rectangle of desired area and shape. Furthermore, this embodiment allows to create a light source having an emission surface Sf which can have any shape, for example a circular or elliptical shape. In what follows, this light source is referred to as a "rectangular beam source". It should be noted that the result is not obtained by relying on an aperture made with a blade and an image forming optics, as occurs, for example, in standard stage lighting projectors, of the theatrical type, in which the cutting of the beam results in high transmission losses. Therefore, the rectangular beam source allows the overall energy consumption to be minimized.

Although not illustrated, a different embodiment is possible, in which the first light source comprises a plurality of emission devices, each of which is formed by a square-shaped LED source and a corresponding square-type compound parabolic concentrator , which has a square inlet opening and a square outlet opening. In this way, each emission device generates a square beam, which has the same divergence in the two orthogonal directions (that is, in the two planes containing the axis of the concentrator and, respectively, the two planes of the outlet opening which are parallel on the sides of the outlet opening). In particular, the present embodiment allows to generate a square beam with a desired divergence, for an arbitrary shape of the emission surface Sf. In what follows, this first light source will be referred to as the "square beam source".

In a further different embodiment (not shown), the first light source comprises a plurality of emission devices, each of which is formed by a LED source having a corresponding circular compound parabolic concentrator (not shown), which has a circular inlet opening and a circular outlet opening. In this case, the first light source generates a beam with a circular symmetry. Therefore, this first light source allows to generate a circular beam with a desired divergence, for an arbitrary shape of the emission surface Sf. In what follows, this first light source will be referred to as the "circular beam source".

In the case in which the reflecting system 20 is made with one or more flat mirrors, or in the case in which the reflecting system 20 includes a single mirror having the shape of a parabolic cylinder, the rectangular beam source allows to obtain a luminous disk SP which is elongated along the y axis, that is a luminous disc SP which circumscribes the first surface S1 of the first diffuser panel 4, the first surface S1 having the shape of an elongated rectangle along the y axis. In both cases, the rectangular beam source is oriented in such a way that its axis of greatest divergence 58 is "mapped" by the reflecting system 20 onto the y axis, so as to reduce the complexity of the configuration of the reflecting system. In the context of the present invention, it is believed that the reflecting system maps the axis of greatest divergence on the y axis if, given a narrow beam of light rays comprising the carrier ray, which originates in the center of gravity O "of the emission surface Sfe it located in the plane of greatest divergence, the reflecting system 20 causes the beam of rays to cross the first diffuser panel 4 along a line tangent to the y axis. For example, if the reflecting system 20 is such that the carrier ray It is folded into a single plane, the rectangular beam source is oriented with the axis of greatest divergence 58 parallel to the y axis.

In the event that the reflecting system 20 comprises two mirrors having parabolic cylinder shapes having orthogonal cylinder axes, it is advantageous to use the square beam source. In this case, in fact, it is possible to rely on the fact that the initial divergence of a square beam is reduced in two different distances from the first light source 2, in order to obtain a luminous disk SP stretched along the y axis. This embodiment allows to achieve an optimal coupling between commercially available LED emitters, which are typically square in shape, and the concentrators.

Furthermore, when the reflecting system 20 comprises a mirror having the shape of a circular paraboloid, the use of the circular beam source is advantageous. In this case, however, the light source 2 can be constituted by a single circular CPC, which is coupled to a circular LED group, this solution allowing to obtain a circular emission surface Sf.

Figure 10 illustrates an additional embodiment, in which the first light source 2 is again formed by identical CPC concentrators 54, the respective inlet openings IN and the outlet openings OUT again being rectangular in shape, by way of example. In this case, however, a mask 60 is applied over the entire opening formed by the outlet openings OUT; mask 60, located in the output plane P_OUT, defines a mask aperture 62, having a shape which is a rounded rectangle with an area greater than the area of a single output aperture OUT. In particular, the mask 60 can be formed by a layer of optically absorbing material, so that the radiation can pass through the output plane P_OUT only through the mask aperture 62. In this way, the first light source 2 is still perceived as having substantially a circular emission surface Sf. The Applicant has also noted that the mask 60 does not substantially distort the shape of the luminous disc SP formed in the plane of the first surface S1.

Regardless of the number and shape of the mirrors forming the reflecting system 20, the lighting system 1 can include a second light source, which comprises a diffused light emission layer, this layer being transparent or at least partially transparent. In use, the further light source emits diffuse light from the emission layer, regardless of whether it is illuminated by the first light source 2, while an observer looking through the diffuse light emission layer of the second light source can see the first light source 2, beyond this emission layer. In the present description, the term "transparent" is used to indicate the so-called optical property of "seeing through", ie the property of an optical element to transmit light that forms images. In particular, considering a light beam generated by a standard D65 point-like illumination source arranged at a considerable distance from the diffused light emission layer (a beam, therefore, consisting of light rays parallel to each other) and directed perpendicularly to the emission layer of scattered light, whereby a portion of the scattered light emission layer is illuminated by a certain beam of rays generated by a standard D65 illuminant, the scattered light emission layer is defined as partially transparent if at least 50%, preferably 70%, more preferably 85% of the light rays of the beam are transmitted by the diffused light emission layer inside a cone with an angular aperture FWHM not greater than 8 °, preferably 4 °, more preferably of 2 °. For the sake of completeness, it should also be noted that the first diffuser panel 4 is also partially transparent.

From a practical point of view, given a standard illuminant (for example, a D65 source) that emits light uniformly from a circular emitting surface, and given a standard observer observing the emitting surface under an 8 ° conical solid angle, preferably of 4 °, more preferably of 2 °, the luminance of the emission surface as perceived by the observer when the partially transparent diffused light emission layer is interposed between the observer and the emission surface, is therefore at least 50%, preferably at least 70%, more preferably at least 85% of the corresponding luminance perceived by the observer when the diffused light emission layer is absent.

Having said all this, as illustrated in Figure 11, the second light source (indicated by the reference number 68) can be arranged parallel to the first diffuser panel 4, for example above it, and for example in direct contact with it.

The second light source 68 may comprise a second diffuser panel 64 and an illuminator 66, the second diffuser panel 64 being shaped as a light guide illuminated from the side by the illuminator 66, the illuminator 66 being formed, for example, by an array linear LED or a fluorescent tube lamp, whereby the light emitted by the illuminator 66 propagates in guided mode inside the second diffuser panel 64, which spreads it homogeneously. The second diffuser panel 64, for example, can be a commercial diffuser suitable for side lighting, such as "Acrylite® LED" or "Plexiglas® LED EndLighten". Also, as shown in Figure 11, the thickness along the H axis of the second diffuser panel 64 is irrelevant to the thickness along a K direction perpendicular to the H axis.

In a particular configuration, the second diffuser panel 64 is formed by a third material (for example, a material selected from the materials listed above with reference to the first material), in which microparticles of a fourth material are dispersed (for example ZnO, TiO2, ZrO2, SiO2, Al2O3); such third and fourth materials do not absorb light with wavelengths in the visible range. In particular, the diameters of the microparticles can vary from 2 Î1⁄4m to 20 Î1⁄4m.

In use, part of the radiation guided by the second diffuser panel 64 exits from the second diffuser panel 64, while it propagates along the second diffuser panel 64, due to the diffusion operated by the microparticles of the fourth material. Since the second diffuser panel 64 has an irrelevant thickness along the H axis with respect to the K direction, the second diffuser panel 64 is basically transparent for the radiation that propagates along the H axis, but functions as a diffuser for the radiation that propagates along the K direction.

Furthermore, assuming that the second diffuser panel 64 is delimited on the upper and lower sides by a third and a fourth surface S3, S4, at least one of said third and fourth surfaces S3, S4 can be surface worked to give roughness. Such roughness contributes to the diffusion operated by the second diffuser panel 64 of the light generated by the illuminator 66, the diffusion process being virtually homogeneous along any direction parallel to the direction K.

In a known way, the roughness can be designed in such a way that a large part of the light generated by the illuminator 66 is diffused mainly through one between the third and fourth surfaces S3, S4e in particular towards the first diffuser panel 4 . In the event that at least one of the third and fourth surfaces S3, S4 presents roughness, no microparticles need to be dispersed in the second diffuser panel 64. In any case, the roughness may be present on both the third and fourth surfaces S3, S4del second diffuser panel 64.

In a different configuration, the second light source 68 includes a substantially transparent emitting surface, which consists of an OLED film. The OLED film is also able to generate diffused light of controlled color and intensity, while being transparent to the light that passes through it along a direction perpendicular to its surface.

The second light source 68 allows to vary the color and intensity of the diffused light component generated by the lighting system 1, basically without varying the color and intensity of the transmitted component. To this end, it is possible to act on the color and intensity of the light emitted by the second light source 68.

For example, in order to reproduce the characteristics of late afternoon light, it is possible to use a lamp with a low CCT, for example of 2500 K, as the first light source 2; in this way, the color of the transmitted component is similar to the color of sunlight before sunset. Without the second light source 68, the color of the component diffused only by the first diffuser panel 4 could be different from the color of the corresponding natural component. In fact, in nature it happens that the sky above the observer is illuminated by white sunlight, i.e. by sunlight that has not yet passed through the atmosphere, which has a CCT that is approximately equal to 6000 K, a value of far higher than the CCT of the lamp. Consequently, the CCT of the light scattered from the sky above the observer in the late afternoon hours is significantly higher than the CCT of the light scattered by the first diffuser panel 4, in the event that the first light source 2 that illuminates the latter presents a low CCT. However, if the second light source 68 is used, and in particular if the second diffuser panel 64 is used together with the illuminator 66, and if the latter is made up of a set of red, green, blue ("RGB "), It is possible to adjust the luminous flux for each of said three elements; this allows the second diffuser panel 64 to generate a diffuse component having color and intensity that are such that the overall component that comes out of the first diffuser panel 4 and is diffused by the first and second diffuser panels 4, 64, has the desired color . In other words, the second source 68 allows the color of the transmitted component to be decoupled from the color of the diffused component. Furthermore, if a lamp with an adjustable CCT is used as the first light source 2, the variation of natural lighting can be reproduced at different times of the day.

Other embodiments are also possible, in which the second light source 68 is placed under the first diffuser panel 4, so that the light generated by the first light source 2 passes through the first diffuser panel 4 before passing through the second. diffuser panel 64. Furthermore, additional embodiments are possible in which the first and second diffuser panels 4, 64 are physically separated.

Finally, embodiments are also possible in which the second light source 68 is used in the absence of the first diffuser panel 4, that is, in the absence of the Rayleigh panel. In this case, the H axis is a line perpendicular to the scattered light emission layer, which passes through the center of gravity of the scattered light emission layer.

In light of the above, all the embodiments described refer to a system comprising a first light source, a diffused light generator and a dark box, in which the diffused light generator is shaped as a layered component delimited by a inner surface (facing the dark box) and an outer surface (facing the room), and the first light source is configured to emit a visible light beam, and the dark box is optically coupled to the room through the light generator widespread. Furthermore, the scattered light generator is configured to receive the visible light beam, and to be at least partially transparent to the visible light beam, and to transmit at least part of the visible light beam, and to emit diffused light visible from the external surface, and to generate transmitted light with a CCT lower than the CCT of visible scattered light. The scattered light generator can be substantially devoid of chromatic absorption or reflection, that is, it does not absorb or reflect preferably a limited part of the visible light spectrum with respect to another part.

More specifically, the CCT of scattered light is higher than the CCT of transmitted light; more specifically, the CCT of the transmitted light is no higher than the CCT of the light beam generated by the first light source. Furthermore, as already mentioned, in the context of the present invention the light "transmitted" by an optical element is understood as the part of the light rays that strike the optical element and pass through the optical element without undergoing a significant angular deviation, for example being deflected by an angle of less than 0.1 °. Therefore, it is believed that an optical component "transmits at least part" of an incident light beam when it generates a transmitted light component.

As explained above, the scattered light generator can be formed by a Rayleigh diffusion layer, i.e. a layer that selectively diffuses the short wavelength component of the light radiation coming from a main light source, this diffusion layer of Rayleigh being shaped, for example as a flat panel (as in the case of the first diffuser panel 4) or as a curved panel (not shown). In addition, or alternatively, the scattered light generator can be formed by a scattered light source, ie a light source that emits scattered light from an extended layer orthogonal to the H axis, regardless of the light received from the main light source. If only the diffused light source is used, this source is not used to correct the color of the diffused light produced, for example, by the first diffuser panel 4, but to generate the entire diffused component of the light emitted by the lighting system. . In some embodiments, the scattered light generator can have an elongated shape, in the sense that a first circle inscribed in the inner surface has a diameter at least 1.5 times smaller, preferably twice less, than a second circle circumscribed thereon. inner surface.

The advantages brought by the present lighting system have been highlighted by the previous description.

In detail, the present lighting system allows an observer to perceive the presence of an unlimited space beyond the diffused light generator, similar to what happens in nature when the sky and the sun illuminate a room through a window. This result is due to the presence of the dark box, which is coupled to the room by means of the diffused light generator. The dark box allows you to perceive a homogeneous black background for any direction along which the first and / or second diffuser panel is observed. Furthermore, this effect is improved by adopting an appropriate observer-source distance (and therefore a first and / or second panel-source distance) and / or by using a reflecting system that reflects the light rays in such a way that they have a limited range of inclinations. .

Furthermore, some embodiments of the present invention increase the aforementioned breakthrough effect while limiting the space occupied by the lighting system. In particular, the embodiment illustrated in Figure 2 is a staggered lighting system, i.e. a system in which the light source and the first diffuser panel are not aligned, which allows to reduce the space occupied by the system itself, without compromise the quality of lighting.

Finally, it is evident that it is possible to make modifications and variations to the present lighting system, without departing from the scope of protection of the present invention, as defined by the attached claims.

For example, the position of the light source with respect to the focus (s) of the optical elements of the reflecting system may be different from that described. Also, instead of, or in addition to, a converging mirror, the reflective system may include a diverging mirror. In addition, in order to achieve complete removal of the divergence, at least along the direction of the y axis, it is possible to consider more complex mirror shapes (for example, free shape shapes).

Claims (29)

CLAIMS 1. Lighting system for illuminating (1) an environment (6) with lighting that simulates natural lighting, which includes: - a first light source (2) configured to emit a visible light beam; - a diffused light generator (4; 68) delimited by an internal surface (S1, S3), suitable for receiving the light beam, and by an external surface (S2), said diffused light generator being at least partially transparent to the light beam being able to transmit at least part of the light beam and also being able to emit, through the external surface, visible scattered light, the correlated color temperature (CCT) of the transmitted light being lower than the CCT of the visible scattered light; characterized in that it further comprises a dark box (10) which contains the first light source and is capable of being optically coupled to the environment through the diffused light generator. Lighting system according to claim 1, wherein the scattered light generator (4; 68) is such that the CCT of the transmitted light is not higher than the CCT of the light beam. Lighting system according to claim 1 or 2, wherein the scattered light generator (4; 68) is such that the CCT of the visible scattered light is greater than the CCT of the light beam. 4. Lighting system according to any one of the preceding claims, wherein the scattered light generator (4; 68) is arranged with respect to the first light source (2) in such a way that the relation applies at least for a point on the internal surface (S1) spaced by X from a center of gravity (O) on the internal surface (S1, S3), where: - Î ̧1Ã ̈ the angle with which a first light ray of the light beam, which originates from the center of gravity (O ") of an emission surface (Sf) of the first light source, affects the center of gravity of the internal surface; - Î ̧2Ã ̈ the angle with which a second light ray, which originates from the center of gravity of the emission surface of the first light source, affects said at least one point of the internal surface; And - L is equal to or greater than three meters. 5. Lighting system according to any one of the preceding claims, in which the first light source (2) is arranged offset with respect to a line (H) perpendicular to the internal surface (S1, S3) and passing through the center of gravity (O) of the inner surface (S1, S3). 6. Lighting system according to claim 5, further comprising a reflecting optical system (20) arranged inside the dark box (10) and able to convey the light beam on the internal surface (S1, S3), said reflecting optical system being such that the light rays coming, in use, from the internal surface and incident on the reflecting optical system are not reflected on the internal surface. Illumination system according to claim 6, wherein the reflecting optical system (20) comprises a first mirror (22) of the planar type. 8. Lighting system according to claim 7, wherein said first mirror (22) is arranged parallel to the internal surface (S1, S3), in such a way that a projection of the first mirror onto a plane containing the internal surface does not overlaps the inner surface. Illumination system according to claim 6, wherein the reflecting optical system (20) comprises a first mirror (22; 24) of the converging type. Illumination system according to claim 9, wherein the first mirror (22) is shaped as a part of a circular paraboloid. Illumination system according to claim 9, wherein the first mirror (22) is shaped as a part of a parabolic cylinder. Illumination system according to claim 11, wherein the reflecting optical system (20) further comprises a second mirror (24) shaped as a part of a parabolic cylinder, the axes of the first and second mirrors being substantially orthogonal to each other. Illumination system according to claim 12, wherein the first and second mirrors (22; 24) are arranged to share a common focus, the first light source (2) being arranged substantially in the common focus. Illumination system according to any one of claims 6 to 13, wherein the reflecting optical system (20) forms an optical path connecting the first light source (2) to the inner surface (S1, S3), the first mirror ( 22) causing a last curve of the light path before the inner surface (S1, S3); and in which a light beam connecting a center of gravity (O ') of the first mirror to a center of gravity (O) of the inner surface through the reflecting optical system forms an angle within the range of 40 ° to 65 °, both inclusive, with respect to to a direction perpendicular to the inner surface in the center of gravity of the inner surface. Lighting system according to any one of the preceding claims, wherein the first light source (2) is formed by a plurality of light emitting devices (52) and by a plurality of reflecting concentrators (54), each reflecting concentrator being funnel-shaped and having an inlet opening (IN) and an outlet opening (OUT), the area of the inlet opening being smaller than the area of the outlet opening, each light emitting device being optically coupled to the inlet opening of a respective reflecting concentrator. Illumination system according to claim 15, wherein the outlet opening (OUT) of each reflective concentrator (54) is in the shape of a rectangle. Lighting system according to any one of claims 6 to 14, wherein the first light source (2) is formed by a plurality of light emitting devices (52) and by a plurality of reflecting concentrators (54), each reflecting concentrator being funnel-shaped and having an inlet opening (IN) and an outlet opening (OUT), the area of the inlet opening being smaller than the area of the outlet opening, each emitting device of light being optically coupled to the inlet opening of a respective reflecting concentrator; and in which the outlet openings (OUT) are elongated along an elongation direction (57), said light beam having an axis of maximum divergence (58), the reflecting optical system (20) being such that, in use, a beam of light rays, which propagate from the center of gravity (O ") of an emission surface (Sf) of the first light source (2) and lie in the plane of maximum divergence, affects the internal surface (S1, S3) along a line tangent to an axis (y) that passes through the center of gravity of the internal surface and is perpendicular to the plane of incidence of a carrier beam on the first mirror, the carrier beam being the light beam that connects the center of gravity of the emission surface to the center of gravity of the surface internal, through the reflective optical system. 18. Lighting system according to claim 17, wherein the reflecting optical system (20) is configured in such a way that the carrier beam lies in a single plane, and wherein the first light source (2) is arranged in such that said axis of maximum divergence is perpendicular to said single plane. 19. Lighting system according to any one of claims 15 to 18, wherein the first light source (2) further comprises a mask (60) having an overall circular or elliptical aperture (62), said mask being coplanar with said opening apertures outlet (OUT), said mask being suitable for blocking the light coming from the parts of the outlet openings which are arranged around said overall opening. Lighting system according to any one of the preceding claims, wherein the scattered light generator comprises a first diffuser (4) configured not to substantially absorb the light in the visible range and to more effectively scatter the short wavelength components compared to the long wavelength components of the light beam. 21. Lighting system according to claim 20, wherein the first diffuser (4) comprises a matrix of a first material in which first particles of a second material are dispersed, said first and second material having, respectively, a first and a second refractive index, said first particles having equivalent diameters such that the product of said equivalent diameters multiplied by the first refractive index is included in the interval 5 nm-350 nm. 22. Lighting system according to claim 21, wherein the first light source (2) and the density of the particle distribution through the first diffuser (4) are such that the product between the density and the illuminance provided on the first diffuser from the first light source, when in use, is substantially constant on the first diffuser. 23. Lighting system according to any one of claims 20 to 22, wherein said first diffuser (4) has a panel shape, at least one of said internal and external surfaces (S1, S3) being formed by the first diffuser. Lighting system according to any one of the preceding claims, wherein the scattered light generator comprises a second light source (68) configured to emit at least a part of said visible scattered light independently of the first light source (2). Lighting system according to claim 24, wherein the second light source (68) comprises: - a second diffuser (64) shaped like a panel that guides light and is configured to illuminate on board; and - an illuminator (66) to illuminate the second diffuser (64) from the side. Lighting system according to claim 25, wherein the CCT of at least one of the first light source (2) and the illuminator (66) is controllably variable. Lighting system according to any one of claims 24 to 26, wherein the second light source (68) comprises an OLED. 28. Lighting system according to any one of the preceding claims, wherein the scattered light generator (4; 68) has an elongated shape. 29. Building comprising the lighting system (1) according to any one of the preceding claims and a wall (P2) of said environment (6), in which said wall forms a cavity (8), the diffused light generator (4; 68) ) extending into the cavity (8).